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Most planets in the solar system, such as
the
Earth and Jupiter, have strong global magnetic fields that deflect the
solar
wind around the planet. Mars and the Moon are two planetary bodies
without
present-day global magnetic fields, but measurements from the Lunar
Prospector
and Mars Global Surveyor spacecraft, using a novel remote-sensing
method of
detecting planetary magnetic field discovered serendipitously by the
Apollo15
& 16 Subsatellites, have provided maps that show intricate patterns
in
near-surface magnetic fields of these two bodies. The near-surface
fields on
Mars appear to be due to the magnetizing of the planetary crust by
a strong ancient global magnetic field that disappeared about 4.1
billion years
ago. Observations from other Mars missions (such as the Mars Rovers)
indicate
that liquid water was present on the Mars surface in ancient times,
implying a much
thicker atmosphere than at present. An interesting hypothesis for the
disappearance of this thick atmosphere is that once the strong global
magnetic
field disappeared, the solar wind was able to penetrate into the
Martian
atmosphere and scour it away. I will describe the MAVEN (Mars
Atmosphere and
Volatiles EvolutioN) Mars Scout mission (presently being developed for
a 2013
launch) that is designed to find out what physical processes led to the
loss
of atmosphere from Mars, and how effective these processes might have
been when
the Sun was young and much more active than at present.

Biography

Bob Lin

Professor of Physics,
University of California, Berkeley

Bob
Lin isa Professor of Physics at the
University of California, Berkeley, and a world-renowned experimental
space
physicist, with broad research interests ranging from solar and
heliospheric physics,
to lunar and planetary science.His
primary
interest is in how particles are accelerated to high energies in
nature.
He has developed and flown numerous, innovative instruments on NASA
missions to
directly measure the plasma, fields, and energetic particles in regions
where particle
acceleration is occurring; and to do imaging and spectroscopy of the
x-rays and
gamma-rays emitted by energetic particles at the Sun. As part of the
Apollo program,
he and his colleagues developed the Apollo15 & 16 Subsatellites
that were
left in lunar orbit to probe the behavior of the Earth’s distant
magnetotail, and
serendipitously discovered a new method to detect planetary magnetic
fields
remotely, using the magnetic reflection of electrons. He applied this
method on
the Lunar Prospector and the Mars Global Surveyor missions to map the
crustal
magnetic fields of the Moon and Mars, respectively, with extremely high
sensitivity.

Bob
received his B.S. (1962) from Caltech and Ph.D.
(1967) in Physics from the University of California, Berkeley (UCB).He served as Director of the UCB Space
Sciences Laboratory at Berkeley from 1998 to 2008. He has received
numerous
awards and honors, including the George Ellery Hale Prize of the
American
Astronomical Society, and an honorary Docteur
Honoris Causa de l’Universite de Toulouse, as well as many NASA
achievement awards. He is a member of the National Academy of Sciences
and of the
American Academy of Arts and Sciences, and a Fellow of the American
Geophysical
Union.Bob
currently serves on the Editorial Boards of the Space Science Reviews,
Solar
Physics, and Annual Reviews of Astronomy & Astrophysics; and he is
the
Principal Investigator for the RHESSI (Ramaty High Energy Solar
Spectroscopic
Imager) Small Explorer mission and for the Wind 3D Plasma &
Energetic
Particles instrument, and Deputy PI for the MAVEN (Mars Atmosphere
&
Volatiles EvolutioN) Mars Scout mission planned for launch in 2013.